1 files changed, 60 insertions, 0 deletions

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 93aba78dc8b6..89fee2dcb039 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -523,6 +523,66 @@ EXPORT_SYMBOL_GPL(add_memory);
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /*
+ * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
+ * set and the size of the free page is given by page_order(). Using this,
+ * the function determines if the pageblock contains only free pages.
+ * Due to buddy contraints, a free page at least the size of a pageblock will
+ * be located at the start of the pageblock
+ */
+static inline int pageblock_free(struct page *page)
+{
+        return PageBuddy(page) && page_order(page) >= pageblock_order;
+}
+
+/* Return the start of the next active pageblock after a given page */
+static struct page *next_active_pageblock(struct page *page)
+{
+        int pageblocks_stride;
+
+        /* Ensure the starting page is pageblock-aligned */
+        BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));
+
+        /* Move forward by at least 1 * pageblock_nr_pages */
+        pageblocks_stride = 1;
+
+        /* If the entire pageblock is free, move to the end of free page */
+        if (pageblock_free(page))
+                pageblocks_stride += page_order(page) - pageblock_order;
+
+        return page + (pageblocks_stride * pageblock_nr_pages);
+}
+
+/* Checks if this range of memory is likely to be hot-removable. */
+int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
+{
+        int type;
+        struct page *page = pfn_to_page(start_pfn);
+        struct page *end_page = page + nr_pages;
+
+        /* Check the starting page of each pageblock within the range */
+        for (; page < end_page; page = next_active_pageblock(page)) {
+                type = get_pageblock_migratetype(page);
+
+                /*
+                 * A pageblock containing MOVABLE or free pages is considered
+                 * removable
+                 */
+                if (type != MIGRATE_MOVABLE && !pageblock_free(page))
+                        return 0;
+
+                /*
+                 * A pageblock starting with a PageReserved page is not
+                 * considered removable.
+                 */
+                if (PageReserved(page))
+                        return 0;
+        }
+
+        /* All pageblocks in the memory block are likely to be hot-removable */
+        return 1;
+}
+
+/*
  * Confirm all pages in a range [start, end) is belongs to the same zone.
  */
 static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)